Perforating gun system with fluid bypass

ABSTRACT

A method and system for preparing or treating a wellbore in conjunction with a perforating operation. The disclosed perforating gun system includes one or more perforating guns between an uphole flow sub and a downhole flow sub. The uphole flow sub and the downhole flow sub are connected by a fluid bypass that permits fluid to be pumped into the wellbore below the perforating guns. Before perforation, formation-compatible fluid may be pumped through the first and second flow subs via the fluid bypass to displace fluid and debris that may interfere with or cause unwanted damage during perforation. Alternatively, the fluid may be a treating fluid selected to dissolve debris within the wellbore. Following perforation, the fluid may be circulated through the wellbore to remove or dissolve debris created during the perforating process.

BACKGROUND OF THE INVENTION

After drilling the various sections of a wellbore through a subterranean formation, individual lengths of relatively large diameter metal tubulars are typically secured together to form a casing string that is positioned within the wellbore. The casing string increases the integrity of the wellbore and provides a path for communicating fluids from the producing intervals of the subterranean formation to the surface. Conventionally, the casing string is cemented within the wellbore.

For the wellbore to produce, hydraulic openings or perforations must be made through the casing string and the cement and extend into the formation. Typically, these perforations are created by detonating a series of shaped charges disposed within the casing string, adjacent to the producing interval of the formation. Specifically, one or more perforating guns are loaded with shaped charges connected to a detonator via a detonating cord. The perforating guns are lowered into the cased wellbore at the end of a tubing string, wireline, slick line, coil tubing or other conveyance. Once the perforating guns are properly positioned in the wellbore such that the shaped charges are adjacent to the producing interval of the formation, the shaped charges may be detonated, thereby creating the desired hydraulic openings.

In addition to creating hydraulic openings, detonation may cause fluids or particles located within the wellbore prior to detonation to be forced into the formation. In some cases, this may lead to unintentional damage to the formation and impaired hydrocarbon production.

To avoid this unintended damage, the section of the wellbore adjacent to the formation may be prepared for perforation by circulating various fluids through the wellbore. For example, a formation-compatible fluid may be pumped into the wellbore to displace fluids or particles from earlier drilling operations. Displacement is typically accomplished by pumping a formation-compatible fluid into the wellbore downhole of the location to be perforated. As the formation-compatible fluid is pumped into the wellbore, it forces fluid and particles in the wellbore uphole, sweeping out any unwanted fluid or debris in the wellbore prior to pumping.

Alternatively, a treating fluid, such as an acid, may be circulated through the wellbore prior to perforation. Generally, this process involves pumping the treating fluid into the wellbore, allowing it to “soak” and dissolve material within the wellbore, and then pumping the treating fluid and dissolved material to the surface. Treating fluids may also be used after perforation to dissolve debris created by perforation or to stimulate production by increasing the permeability of the formation.

Preparation of the perforating environment through displacement or other treatment generally improves the predictability of perforating operations and protects the formation from unintended damage during perforation. Similarly, treatment after perforation can also improve overall productivity of a well. However, such preparation and treatment often carries additional costs and risks to the wellbore because preparation and treatment often require extra tubing runs or drilling in addition to the perforating process. Therefore, a need exists for an apparatus and method for preparing a perforating environment or stimulating a formation after perforation that avoids unnecessary pipe runs or drilling.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present embodiments and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings, in which like reference numbers indicate like features.

FIG. 1 is a schematic of a perforating gun system with a fluid bypass according to aspects of the present disclosure.

FIG. 2 is a schematic of the perforating gun system of FIG. 1 indicating the flow path of a fluid through the perforating gun system.

While embodiments of this disclosure have been depicted and described and are defined by reference to exemplary embodiments of the disclosure, such references do not imply a limitation on the disclosure, and no such limitation is to be inferred. The subject matter disclosed is capable of considerable modification, alteration, and equivalents in form and function, as will occur to those skilled in the pertinent art and having the benefit of this disclosure. The depicted and described embodiments of this disclosure are examples only, and not exhaustive of the scope of the disclosure.

DETAILED DESCRIPTION

The present disclosure relates generally to downhole drilling operations and work overs. More particularly, the disclosure relates to a perforating gun system with a fluid bypass for circulating fluids through a wellbore.

Illustrative embodiments of the present disclosure are described in detail herein.

In the interest of clarity, not all features of an actual implementation may be described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions are made to achieve the specific implementation goals, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of the present disclosure.

To facilitate a better understanding of the present disclosure, the following examples of certain embodiments are given. In no way should the following examples be read to limit or define the scope of the disclosure. Embodiments of the present disclosure may be applicable to horizontal, vertical, deviated, or otherwise nonlinear wellbores in any type of subterranean formation. Embodiments may be applicable to injection wells as well as production wells, including hydrocarbon wells.

FIG. 1 is a diagram showing a perforating gun system according to one embodiment. The perforating gun system 100 is shown in a section of a wellbore 101 in which casing 102 has been cemented in place. Specifically, the perforating gun system 100 is shown in a position within the wellbore 101 corresponding to a zone of a formation to be perforated.

The perforating gun system 100 is installed on the distal end of a section of hollow tubing 104 with a coupler 106. Downhole from the coupler 106 is an uphole flow sub 108, a series of perforating guns 110A-C, and a downhole flow sub 111. A pair of fluid bypasses 112A-B connect the uphole flow sub 108 and the downhole flow sub 111.

Following drilling of the wellbore 101 and installation of the casing 102, the perforating gun system 100 is inserted into the wellbore 101 and positioned in a zone to be perforated. Perforation is typically accomplished by detonating a series of shaped charges (not depicted) within the perforating guns 110A-C. Ports on the guns 110A-C, such as port 113, direct the energy of the detonated charges into the formation, perforating the casing, the cement, and a portion of the zone to be perforated thereby creating hydraulic openings for fluid to communicate between the wellbore and the formation.

In addition to creating hydraulic openings between the wellbore and the formation, detonation of the charges may force fluids, such as drilling mud, brine, cement, or other fluids used in drilling and completion operations, from within the wellbore into the surrounding formation. This may lead to unintended damage to the formation and negatively affect hydrocarbon production.

To avoid this damage, the wellbore section adjacent to the zone to be perforated be prepared for perforation by circulating a formation-compatible fluid through the wellbore, displacing any other fluids or debris that may be present, or by circulating a treating fluid for dissolving and removing debris or other potentially harmful material.

As depicted in FIG. 2, circulation is achieved by pumping a fluid through tubing 104 into the uphole flow sub 108. The fluid is diverted through the fluid bypasses 112A-B and into the downhole flow sub 111. The fluid then exits the downhole flow sub 111 via one or more fluid outlets 114, and enters the wellbore 101 below the zone to be perforated.

In displacement applications, as fluid is pumped into the wellbore 101, the fluid travels up the wellbore between the perforating gun system 100 and the casing 102, displacing any other fluid within the zone to be perforated. In applications where the fluid is intended to dissolve material within the wellbore, the fluid is pumped into the wellbore, left to dissolve material within the wellbore, and then pumped out of the wellbore along with the entrained dissolved material. Following a displacement or dissolution operation, perforation may be performed.

Treating or stimulation fluid may also be circulated through the wellbore via the perforating gun system after perforation has occurred. Because hydraulic openings now exists between the wellbore and the formation, the treating or stimulation fluid may enter the formation and may be used to dissolve debris or formation damage created during perforation or to stimulate production by increasing the permeability of the formation

Although the fluid bypasses 112A-B are depicted in FIGS. 1 and 2 as a pair of tubes running along the outside of the guns 110A-C, other embodiments may include other arrangements and configurations of fluid bypasses. For example, embodiments may include any number of bypasses, one or more of which may run along any suitable path between the first flow sub 108 and the second flow sub 111, including through the perforating guns.

The particular embodiments disclosed above are illustrative only. as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the present invention. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. The indefinite articles “a” or “an,” as used in the claims, are each defined herein to mean one or more than one of the element that it introduces. 

What is claimed is:
 1. A perforating gun system, comprising a first flow sub disposed on a proximal end of the perforating gun system; a second flow sub disposed on a distal end of the perforating gun system, the second flow sub comprising a fluid outlet; one or more perforating guns disposed between the first flow sub and the second flow sub; and a fluid bypass connecting the first flow sub to the second flow sub, wherein the first flow sub, the second flow sub, and the fluid bypass define a fluid flow path between the first flow sub and the fluid outlet.
 2. The perforating gun system of claim 1, wherein the fluid bypass is external to the one or more perforating guns.
 3. The perforating gun system of claim 1, wherein the fluid bypass extends through the one or more perforating guns.
 4. The perforating gun system of claim 1, further comprising a coupler connected to a proximal end of first flow sub, the coupler configured to connect to at least one of a tubing string and coiled tubing.
 5. The perforating gun system of claim 1, wherein the one or more perforating guns further comprise one or more charges and one or more ports configured to focus energy released during detonation of the one or more charges.
 6. The perforating gun system of claim 1, further comprising a second fluid bypass connecting the first flow sub to the second flow sub, wherein the first flow sub, the second flow sub and the second fluid bypass define a second fluid flow path between the first flow sub and the fluid outlet.
 7. A downhole tool, comprising: a first flow sub disposed on a proximal end of the downhole tool; a second flow sub disposed on a distal end of the downhole tool comprising a fluid outlet, wherein the downhole tool is configured to receive one or more perforating guns between the first flow sub and the second flow sub; and a fluid bypass connecting the first flow sub to the second flow sub, wherein the first flow sub, the second flow sub, and the fluid bypass define a fluid flow path between the first flow sub and the fluid outlet.
 8. The downhole tool of claim 7, further comprising a coupler connected to a proximal end of the first flow sub, the coupler configured to connect to at least one of a tubing string and coiled tubing.
 9. The downhole tool of claim 7, further comprising a second fluid bypass connecting the first flow sub to the second flow sub, wherein the first flow sub, the second flow sub and the second fluid bypass define a second fluid flow path between the first flow sub and the fluid outlet.
 10. A method, comprising: inserting a perforating gun system into a wellbore extending through a formation, the perforating gun system comprising a first flow sub; a second flow sub, the second flow sub comprising a fluid outlet; one or more perforating guns disposed between the first flow sub and the second flow sub; and a fluid bypass connecting the first fluid sub to the second fluid sub, wherein the fluid bypass defines a fluid flow path between the first fluid sub and the second fluid sub; locating the perforating gun system at a location within the wellbore to be perforated; and circulating a first fluid through the fluid flow path such that the first fluid exits the second fluid sub via the fluid outlet.
 11. The method of claim 10 wherein the first fluid is one of the group of a formation-compatible fluid for displacing other fluid in the wellbore, a treatment fluid suitable for dissolving debris within the wellbore, and a stimulating fluid for increasing permeability of the formation.
 12. The method of claim 10 further comprising circulating a second fluid through the fluid flow path such that the second fluid exits the second fluid sub via the fluid outlet.
 13. The method of claim 10, further comprising perforating the wellbore with the one or more perforating guns.
 14. The method of claim 13 wherein the first fluid is circulated before perforating the wellbore.
 15. The method of claim 13 wherein the first fluid is circulated after perforating the wellbore.
 16. The method of claim 13 further comprising circulating a second fluid through the fluid flow path such that the second fluid exits the second fluid sub via the fluid outlet, wherein the first fluid is circulated before perforating the wellbore and the second fluid is circulated after perforating the wellbore. 